- 學位論文
烘焙時間及溫度對於蘇門答臘咖啡（C. arabica）的最優抗氧活性
Roasting Time and Temperature for Optimal Antioxidant Activity in Sumatran Coffee (C. arabica)
摘要
咖啡中含有豐富的抗氧化物質能預防人體遭受活性氧的損害，咖啡中主要的抗氧化物質主要是酚醛，於咖啡烘培的過程當中轉變成風味及顏色的物質。本研究探討咖啡烘焙過程中抗氧化能力變化，找出最適烘焙條件。本實驗設計採中央合成設計實驗(central composite design)，將蘇門答臘濕剝咖啡豆以不同時間（9.6, 10, 11, 12, 12.4 分鐘）及溫度(196.5, 200, 209, 217, 220.5℃) ，共13組實驗。以Agtron Gourmet 與 Hunter L, a, b 量測烘培色澤為中焙和深焙（±1% 水分）。顔色黃和紅色之顏色減少。當烘焙溫度愈高咖啡豆的重量損耗愈多，而清除DPPH自由基能力、還原力和總酚化合物含量愈低。從清除自由基與總還力結果上得知，總酚類化合物含量的降解與抗氧化能力的降低有密切關係。結果顯示只有烘焙溫度具統計意義。最適化結果為將蘇門答臘咖啡豆烘焙11分鐘到200℃。將最適化結果進行感官品評(n = 30位)，結果表明烘焙12分鐘到200℃，有較佳抗氧能力和接受度，其抗氧化能力為：78.12 ± 0.60% DPPH自由基清除能力，1.29 ± 0.10還原力，和80.38 ± 0.84 mg GAE/kg總酚含量。
並列摘要
Coffee is a very common drink with antioxidant properties that reduce the health-damaging effects of free radicals. Most of the antioxidant properties in coffee come from the phenolic fraction of its phytochemical composition; some of which become flavoring and coloring compounds during roasting. This study intended to find the combination of roasting time and temperature to obtain optimal antioxidant activity in Sumatran Arabica coffee. Sumatran wet-hulled coffee beans were roasted under 13 combinations of target temperature (196.5, 200, 209, 217, 220.5℃) and time (9.6, 10, 11, 12, 12.4 minutes) using the central composite design. The products of the experiment measured on the Agtron Gourmet scale of roast degree as medium and dark roasts. Beans roasted to higher temperatures lost more weight and had less red and yellow undertones. In general, the same condition also leads to lower levels of antioxidant activity in terms of 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity, Folin-Ciocalteu total phenolic content, and ferric reducing power. Antioxidant activity in terms of radical scavenging and ionic reduction are closely linked to the phenolic fraction of coffee and its thermal degradation. In the response modelling for DPPH free radical scavenging activity, ferric reducing power, and total phenolic content, only roasting temperature had a statistically significant effect. The roasting condition for optimal antioxidant activity in Sumatran coffee beans was found to be roasting to 200 degrees in 11 minutes. However, sensory evaluation (n = 30) of the optimized product and selected experimental combinations revealed that the roasting condition for high antioxidant activity and acceptable flavor is roasting to 200C for 12 minutes to a Full City roast (Agtron Gourmet 41-50). Coffee beans roasted with this time-temperature combination had 78.12 ± 0.60% of DPPH free radical scavenging activity, 1.29 ± 0.10 units of ferric reducing power, and a total phenolic content of 80.38 ± 0.84 mg GAE/kg dry mass.